Antiknock agent



April 1946. E. BARTHOLOMEW 2,398,282

' ANTIKNOGK AGENT 7 Filed Nov 27, 1944 GQAMS 5 40 GRAMS IRON R 3.18 GRAMS LEAD [68 GQAMS IRON 5 [06 694515 LEAD 2.52 GRAMS IEON 2.52 GRAMS IRON T 2.65 GQAMS LEAD we (/.0) TETRA Al/(Yt 1540,6940 (40 PAW GAILO/V INVENTOR.

{FIGURES //V PARENTHESEj 4P5 CC. 7571645 7/1 YL LEAD/ Patented Apr. 9, 1946 an'rnmocx AGENT Earl Bartholomew, Birmingham, Mich., asslgnor to Ethyl Corporation, poration of Delaware New York, N. Y., a cor- Application November 27, 1944, Serial No. 565,200-

Claims.

This invention relates to antiknock compounds. Many attempts have been made to use iron carbonyl as an antiknock agent in high compression engines, chiefly because it can be manufactured at a lower cost than the lead alkyls.- Some of these attempts have included the use of lead alkyls in very small proportional quantities. These attempts have not had any appreciable success and the reason for this has not been clear. So far as I am aware these attempts have been based on a primary consideration of the use of iron carbonyl, and other factors were wholly secondary to this.

This application is a continuation-in-part of my application, Serial No. 490,659, filed June 12, 1943, for Antiknock agent. r

The use of either a lead alkyl or iron pentacarbonyl alone in a motor fuel gives a beneficial result and it would be presumed that the use of the two together would give a result which could be predetermined from a knowledge of the antiknock properties of the individual compounds. However, the use of the two together may yield a negative result in that the antiknock eil'ect of a mixture of the two may be less than that of one of them used alone.

I have found that by treating each of the mixtures of iron pentacarbonyl and a lead alkyl as basically a new single antiknock compound, de-

termining the intrinsic antiknock properties and then evaluating these intrinsic antiknock properties in the light of other characteristics of each of the components, I obtain a new and'difierent concept of the utility of mixtures of these two antiknock compounds.

The object of the present invention is to provide useful antiknock mixtures of tetraalkyl lead and iron pentacarbonyl.

The single figure of the drawing is a chart illustrating the antiknock values of different mixtures of tetraalkyl lead and iron pentacarbonyl when added to a widely used commercial base fuel. This fuel was the base for Standard Oil bonyl is indicated as grams of iron per gallon. For convenience the corresponding volumes 0! tetraethyl lead and iron pentacarbonyl are shown in parentheses on the horizontal and vertical scales respectively.

Each line, A to M inclusive, indicates mixtures having a constant antiknock value. Mixtures indicated by line A have the lowest antiknock value and lines lying to the right of A indicate mixtures of progressively higher antiknock value. Each ofthese lines may be used in the following manner, taking line H as an example. This line starts from the horizontal axis at 1.32 grams of lead (1.25 c. c. of, tetraethyl lead) and 0.0 grams ofiron per gallon of fuel, indicating that the fuel contains 1.32 grams of lead and no iron pentacarbonyl. If 0.21 gram of iron (0.5 c. 'c of iron pentacarbonyl) is added to the base fuel, then, to keep the antiknock value of the curve constant, one would expect that less than 1.32 grams of lead would be required and therefore that a point P on the curve having an ordinate of 0.21 gram of iron should lie to the left of the starting point of the curve, as indicated on the chart. In-

stead of passing'to the left through point P, the curve passes to the right of'it through P. This shows that the addition of iron pentacarbonyl has Company of Indiana Red Crown gasoline as sold from 1935 to 1941. The method oftest was the A. S. T. M. method D-357-39 T also known as the A. S. T. M. motor method. The horizontal axis OX indicates the quantity of lead alkyl in the mixture per gallon of fuel and the vertical axis OY'indicates the quantity of iron pentacarbonyl in the mixture per gallon of fuel. Inasmuch as the quantity of lead in a given volume of the dif-' ferent lead alkyls is not constant, the quantity of lead alkyl is indicated as grams of lead per gallon. Likewise the quantity of iron pentacargrams of lead per gallon.

decreased the efiectiveness of the tetraethyl lead and more than 1.32 grams of lead must be used to obtain an antiknock effect equal to that of 1.32 grams of lead alone per allon. On this curve 0.21 gram of iron and 1.46 grams of lead per gallon are equal in antiknock effect to 0.0 c. c. of iron and 1.32 grams of lead per gallon. A mixture of 0.55 gram of iron (1.3 c. c. iron pentacarbonyl) n grams of lead per gallon has the same effect as the 0.0 grams of iron and 1.32 Between these two points on the curve the compounds are so mutually toxic that the addition of'the iron pentacarbonyl results in a'loss of antiknock value and therefore the addition of iron pentacarbonyl is ent in the mixture gives a useful result but at no point on the curve is the value of the mixture equal to the sum of the values of the two constituents. The value of a mixture cannot be predicated upon a knowledge of the values of each of the compounds in the mixtures.

I find that i'useful mixtures of iron pentacarbonyl and tetraalkyl-lead lie within the area bounded by the lines OR, OS, and NR inclusive.

The mixture chosen depends on the cost of the components of the mixture, the increment of antiknock value desired from the mixture, the nature of the base fuel, the type of engine,-the conditions of engine operation and the increased rate of engine wear attributable to the antiknock mixture.

Because of the lower cost of iron pentacarbonyl it would appear that all mixtures should be chosen near the line 05. The lower boiling point,

of iron pentacarbonyl also suggests this inasmuch as the antiknock mixture will be more evenly distributed during periods of poor fuel distribution. When operating engines which tend to preignite I prefer to use mixtures having a relatively high iron pentacarbonyl content because I have found that products of combustion of iron pentacarbonyl which remain in the combustion chamber have less tendency to cause preignition than those of tetraethyl lead. Where engines are run on rich fuel-air mixtures (high fuel content) as during take-oil of airplanes. a relatively high iron pentacarbonyl content is desirable because of the increased effectiveness of iron pentacarbonyl relative to tetraalkyl lead compounds under these conditions.

. I find, however, that certain conditions of engine operation call for a wider range of mixtures than those near the line OS. If an engine may operateunder knocking conditions at high speed or at high mixture or cylinder temperature at low speed, it is desirable to choose mixtures lying farther to the right of line OS on the chart because of the relatively low effectiveness of iron pentacarbonyl and high effectiveness of tetraethyl lead under such conditions when used in admixture. The decrease in effectiveness of iron pentacarbonyl under these conditions is so great as to suggest the possibility of premature decomposition. Under these conditions tetraethyl lead retains its efiectiveness.

On the chart I have shown the effectiveness of mixtures of iron pentacarbonyl and tetraethyl lead up to concentrations of 2.52 grams of iron (6.0 c. c. of iron pentacarbonyl) per gallon so as to indicate the nature of the curves. Iron oxide, formed by the combustion of iron pentacarbonyl, is an abrasive and produces engine wear. I have discovered that this abrasive action is decreased by the use of substantial amounts of lead alkyl antiknock compounds with the iron pentacarbonyl. This effect is barely discernible with ratios near line OS, is pronounced with ratios near line OT, and still greater with ratios near line OR. However, because of excessive engine wear associated with the use of large amounts of iron pentacarbonyl, even when tetraethyl lead is present,

I employ mixtures having an iron pentacarbonyl content of not more than 4.0 c. 0. per gallon, equivalent to 1.68 grams of iron, as indicated by line NR.

- For the above reasons my preferred mixtures for overall-engine operation lie between lines OS and OT inclusive on the chart. For general use, in all types of engines and base fuels under the wide range of weather and driving conditions encountered in service, I prefer to use three parts iron pentacarbonyl by volume with one part tetraethyl lead. This mixture is not critical and small variations in either direction give substantially as its scale of abscissae and grams of iron .as

line OT or to the right of it to inhibit engine wear.

It is well known that diflerent fuels have diflerent susceptibilities to antiknock compounds and the measurement of the susceptibility is a standard procedure. Different fuels also have different effects on the mutual toxicity of tetraethyl lead and iron pentacarbonyl. In general this mutual toxicity is at a maximum in highly aromatic base fuels and at a minimum in highly volatile paramnic fuels. The mutual toxicity tends to become greater as the unsaturation is increased. In all fuels this effect is readily determined by the same standard procedure as is used in measuring antiknock susceptibility. With all of these fuels my mixtures are those described above and defined on the chart by the lines OR, OS, OT, and NR, however, in the case of fuels giving unusually high mutual toxicity, I prefer to use mixtures lying fairly close to line OT.

The curves for mixtures containing other lead alkyls with iron pentacarbonylv may vary from those for mixtures containing iron pentacarbonyl and tetraethyl lead but if they vary the differences are not material as to a choice of the mixture to be used.

Tetraethyl lead is used more widely than any other lead compound as an antiknock and for this reason its use with iron pentaoarbonyl has been described above. The more useful range of lead alkyls for admixture with iron pentacarbonyl appears to extend from lead dimethyl diethyl to the heavier alkyls such as lead tetra-n-butyl.

The usefulness of tetramethyl lead and trimethylethyl lead for antiknock purposes is small in comparison with the other alkyls. Any other lead alkyl can be used in place of or with tetraethyl lead in my mixtures. I

It is well known that halides are used with lead alkyl antiknockcompounds andthey may be used in my mixtures in accordance with the content of lead alkyls present.

I claim:

1. An antiknock mixture of iron pentacarbonyl and a tetraalkyl lead whose proportions, on a chart having grams of lead per gallon of fuel its scale of ordinates, lie within an area bounded by straight lines drawn through the origin and points R and S, having coordinates respectively 3.18 grams lead, 1.68 grams iron and 1.06 grams lead, 2.52 grams iron, and horizontal line NR, whose equation is 3/ equals 1.68, inclusive.

2. An antiknock mixture of iron pentacarbonyl and a tetraalkyl lead whose proportions. on a chart having grams of lead per gallon of fuel as its scale of abscissae and grams of iron as its scale of ordinates, lie within an area bounded by straight lines drawn through the the origin and points T and S, having coordinates respectively 2.65 grams lead, 2.52 grams iron and 1.06 grams lead, 2.52 grams iron. and horizontal scale of abscissae and grains of iron as its scale of ordinates, lie within an area bounded by straight lines drawn through the origin and points It and S, having. coordinates respectively 3.18 grams lead, 1.68 grams iron and 1.06 grams whose equation is 1! equals 1.68, inclusive.

4. An antiknock mixture of iron pentaeslbonyl and tetraethyl lead whose proportions, on a chart having grams of lead per gallon of tuel as its scale of abscissae and grams or iron as its scale of ordinates, lie within an area bounded by straight lines drawn through the origin and spasms 3 lead, 252 grams iron, and horizontal line NR.

points '1. and 8, having coordinates r spectively 2.65 grams load, 2.52 grams iron and 1.06 ms lead, 2.52 grams iron,- and horizontal line NR, whose equation is equals 1.88, inclusive.

5. An antiknock mixture consisting of by volume substantially three partsiron pentacarbonyl and one part tetraethyl lead.

EARL BARTHOLOMEW. 

